1. Field of the Invention
The present invention relates to a free-flowing agglomerated powder detergent containing high levels of nonionic surfactant and a process for making the same.
2. Discussion of Related Art
There is an on-going effort to provide powdered laundry detergents having an increased amount of detergent surfactants. The benefits of highly concentrated detergents include a savings in packaging use and cost. Unfortunately, there are limits to the amount of detergent surfactant that can be included in a powdered detergent while still providing the consumer desired characteristics of flowability, solubility, cleaning and whitening performance.
Most granular detergents are produced by spray drying. This process involves mixing detergent components such as surfactants and builders with water to form a slurry which is then sprayed into a high temperature air stream to evaporate excess water and to form bead-type hollow particles. While spray drying the detergent slurry produces a hollow granular detergent having an excellent solubility, extremely large amounts of heat energy are needed to remove the large amounts of water present in the slurry. Another disadvantage of the spray drying process is that because large scale production equipment is required, a large initial investment is necessary. Further, because the granules obtained by spray drying have a low bulk density, the granule packaging volume is large which increases costs and paper waste. Also, the flowability and appearance of the granules obtained by spray drying may be poor because of the presence of large irregularities on the surface of the granules.
In addition to these characteristic processing and product problems associated with the spray drying process, volatile materials, such as nonionic surfactants, are emitted into the air when processed by this method. This volatilization problem, manifested by the discharge of dense "blue" smoke from the spray tower, is referred to as "pluming." Air pollution standards limit the opacity of the plume. Consequently, it is necessary to limit the capacity of the spray tower or, in extreme instances, discontinue operation.
In an attempt to avoid the problems caused by spray drying, considerable developmental effort has focused on post-dosing the product with nonionic surfactants after the spray drying operation. Unfortunately, post-dosing of the spray dried base with surfactant in amounts sufficient to provide satisfactory wash performance generally results in a product that has poor dissolution characteristics. Accordingly, the amount of surfactant that may be employed in the detergent formulation is severely limited. Because heavy-duty laundry detergents need large amounts of nonionic surfactant present, inorganic silicates have been added to these detergent formulations to absorb the nonionic liquids.
For example, U.S. Pat. No. 3,769,222 to Yurko et al. discloses mixing liquid nonionic surfactants with sodium carbonate until partial solidification occurs followed by the addition of large amounts of silica (silicon dioxide) to produce a dry free-flowing detergent composition. A disadvantage to this technique, however, is that because the silica has no significant cleaning activity, its inclusion in a detergent formulation in large amounts merely serves to increase the cost of the product. Further, the use of silica in detergents adds to the total suspended solids (TSS) content of laundry waste water contrary to the dictates of many local and state water pollution standards. Therefore, there is an incentive to keep low the amount of silica added to the detergent composition.
U.S. Pat. No. 4,473,485 to Greene reports that a free-flowing granular detergent can be prepared by mixing a polycarboxylic structuring agent solution with a micronized carbonate followed by the addition to the mixture of a nonionic surfactant and water, followed by removal of the excess water. The preferred micronized carbonate is calcium or sodium carbonate. A disadvantage of this process, however, is that the micronized carbonate used by Greene to enhance the flowability of the detergent product is quite expensive as compared to standard sodium carbonate. Without the use of the micronized carbonate, Greene's product would not have such good flowability. In addition, where the micronized carbonate is calcium carbonate, the building capability of the detergent is reduced.
Therefore, a need exists for a process and its resulting composition that substantially overcomes the problem of free-flowability in highly loaded nonionic detergents.